# Mihama nuclear power plant reactor shutdown > Live situation record from CLSTR: https://clstr.news/situations/mihama-nuclear-power-plant-reactor-shutdown > Updated: 2026-09-25T10:35:00.000Z. Sources: 2. Developments: 2. On September 17, Kansai Electric Power performed a manual shutdown of the Mihama Nuclear Power Plant Unit 3 in Fukui Prefecture after detecting water droplets leaking from secondary system equipment. The leak, which did not contain radioactive substances, was initially reported as approximately three drops per second. Subsequent investigations identified the cause as a construction error dating back to 2010. A stainless steel protective cover had been installed upside down, allowing rainwater to enter a gap and cause corrosion in a carbon steel pipe. This corrosion resulted in a hole measuring roughly 14mm by 4mm. As a result of the leak, the scheduled resumption of commercial operations for Mihama Unit 3, originally planned for October 9, has been delayed indefinitely. Fukui Prefecture has requested that the company inspect the installation status of covers on all other outdoor piping. ## Timeline ### 2026-09-25: Mihama Nuclear Power Plant Unit 3 shutdown caused by pipe corrosion A construction error from 2010 caused a pipe leak at Mihama Nuclear Power Plant Unit 3, forcing a reactor shutdown. The upside-down protective cover allowed rainwater to corrode the pipe. 2 sources. https://clstr.news/cluster/mihama-nuclear-power-plant-unit-3-shutdown-caused-by-pipe-corrosion ### 2026-09-17: Japanese nuclear plants: Shimane safety showcase and Mihama manual shutdown Chugoku Electric Power aims for a 2030 startup at Shimane Unit 3 following safety inspections, while Kansai Electric Power manually shut down Mihama Unit 3 due to a secondary system water leak. 2 sources. https://clstr.news/cluster/japanese-nuclear-plants-shimane-safety-showcase-and-mihama-manual-shutdown --- Cite as: Mihama nuclear power plant reactor shutdown. CLSTR, https://clstr.news/situations/mihama-nuclear-power-plant-reactor-shutdown